Glow discharges have become invaluable analytical sources for spectrometric applications. Efforts to develop glow discharges that can be sustained at atmospheric pressure have been primarily focused on minimizing the effect of transient instabilities of the electrical field on the surface of the electrodes, either by changing the system geometry or by using alternative powering schemes. Changes to the system geometry are based on similarity laws, which state that the gap between the electrodes must be reduced as the pressure is raised, in order to maintain the stability of the glow regime. At atmospheric pressure, sub-millimeter gaps are typically required, which has led to the development of miniaturized dc glow discharges.
Atmospheric pressure glow discharges can be sustained in a variety of gases, including hydrogen and hydrogen-methane mixtures, oxygen, nitrogen and air. Extensive diagnostic studies on a helium atmospheric-pressure glow discharge have been previously performed, including the determination of the helium metastable concentrations within it, the decay kinetics of excited species in the presence of impurities, and several parameters associated with the cathode fall. Several other studies have described atmospheric-pressure glow discharges of different geometries in air and nitrogen.